Living or working in a noisy environment could increase a person's risk of a heart attack, a study says.

Environmental noise, such as traffic, increased heart attack risk twofold to threefold, a German study in the European Heart Journal found.

Risk appeared to be related to how loud rather than how annoying the noise was, so current noise safety levels may need to be stricter, say the authors.

Experts urged people not to be alarmed, saying more work was needed.

Bad for hearts

Lead researcher Dr Stefan Willich, from the Charité University Medical Centre in Berlin, said: "We seem to be looking at a threshold at which risk occurs and remains constant above this, and this appears to be around 60 decibels."

Sixty decibels is the level of noise typically experienced, for example, in a busy large office.

The researchers compared over 2,000 heart attack patients with over 2,000 control patients admitted to trauma and general surgery departments in Berlin between 1998 and 2001.

Chronic noise exposure was associated with a mildly to moderately increased risk of heart attack.

Safety levels

A mechanism that might explain the link, said Dr Willich, was that noise could increase psychological stress and anger, leading to physiological changes in the body such as increased levels of adrenaline and noradrenaline, which are associated with increased blood pressure and plasma lipids.

"Such mechanism may be further modified by personal parameters - smoking or pressure from meeting deadlines. In that case, chronic noise would be the equivalent of an outside risk factor contributing to atherosclerosis and cardiovascular disease," he explained.

We should definitely be looking at something lower...somewhere between 65 and 75 decibels

Dr Willich

He plans further work, but said in the meantime the current safety cut- off levels of 85 decibels - equivalent to road construction equipment - are too high.

"We should definitely be looking at something lower. The exact value is unclear, but somewhere between 65 and 75 decibels," he said.

In the UK, the current limit is 85-90 decibels. This is set to be lowered to 80-85 decibels in April.

Dr Willich said: "It is particularly important to focus on people with known cardiovascular disease to improve prevention for them, either by not exposing them chronically to heavy noise or by lowering the threshold for protective wear."

Recent research estimates that 170,000 people in the UK suffer deafness, tinnitus or other ear conditions as a result of exposure to excessive noise at work.

In Dr Willich's study, workplace noise levels increased the heart attack risk for men by nearly a third, but did not affect women's risk.

NOISE LEVELS IN DECIBELS

Normal conversation 50-60

A loud radio 65-75

A busy street 78-85

A heavy lorry about 7 metres away 95-100

A pighouse at feeding time 110

A chain saw 115-120

A jet aircraft taking off 25 metres away 140

Belinda Linden, of the British Heart Foundation, said: "We do not want people to be alarmed by the findings of this study. However, it is vital that we explore the wider impact of noise on our lives.

"Past studies have looked at the effects of noise on hearing, heart rate, blood pressure, sleep, mental health and performance. These noise effects in themselves can also indirectly influence heart health.

"There is also difficulty in controlling other influencing factors such as emotion, anger and lack of control. These and other issues, such as noise exposures, which were not evaluated in the study, may make it difficult to precisely measure the noise-induced health effects or compare the results of this study with previous studies.

"This study opens the door to many questions which hopefully will be addressed in the future studies planned by Dr Willich and his team."